Keen Sight and Smell. The owlbear has advantage on Wisdom (Perception) checks that rely on sight or smell.

Senses. Darkvision 60ft

Stench of the Grave. Any creature that starts its turn within 5 feet of the owlbear must succeed on a DC 13 Constitution saving throw or be poisoned until the start of its next turn.

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Multiattack. The owlbear makes two attacks: one with its beak and one with its claws.

Beak. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 10 (2d6 + 5) piercing damage.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (2d10 + 5) slashing damage.

Necrotic Roar (Recharge 5–6). The owlbear lets out a deathly shriek. Each creature within 15 feet must make a DC 14 Constitution saving throw or take 18 (4d8) necrotic damage and be frightened until the end of their next turn. On a success, a creature takes half damage and isn't frightened.